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==Overview==
==Overview==
[[Image:LH sIgA.png|thumb|right|250px|<p>1 = Heavy Chain</p><p>2 = Light chain</p><p>3 = J chain</p><p>4 = Secretory component</p>]]
[[Image:LH sIgA.png|thumb|right|250px|<p>1 = Heavy Chain</p><p>2 = Light chain</p><p>3 = J chain</p><p>4 = Secretory component</p>]]
IgA is a dimeric immunoglobulin that is produced by the joining of two IgA monomers by a ‘J’ chain. Its heavy chain is type alpha(α). There are two types of IgA:
IgA is a dimeric immunoglobulin that is produced by the joining of two IgA monomers by a ‘J’ chain. Its heavy chain is type alpha(α). There are two types of IgA:
'''Type 1''' - Non-secretory and found in blood.
:'''Type 1''' - Non-secretory and found in blood.
:'''Type 2''' – Secretory and secreted on mucosal surfaces.
'''Type 2''' – Secretory and secreted on mucosal surfaces.
Only Type 2 contains the secretory component, a glycoprotein, which protects IgA from digestion and mediates its active transport across mucosal epithelium. The secretory component is added to salivary IgA by mucosal epithelial cells in the salivary glands, while in the alimentary tract, the secretory component is produced by the enterocytes.
Only Type 2 contains the secretory component, a glycoprotein, which protects IgA from digestion and mediates its active transport across mucosal epithelium. The secretory component is added to salivary IgA by mucosal epithelial cells in the salivary glands, while in the alimentary tract, the secretory component is produced by the enterocytes.
==Production==
==Production==
IgA is preferentially produced at mucosal surfaces by plasma cells. Il-4 produced by T cells (Th2) and mast cells, signals B cells to differentiate into plasma cells. Il-10 and CD40 interaction with Th2 cells then causes class switching to produce IgA.
IgA is preferentially produced at mucosal surfaces by plasma cells. IL-4 produced by T cells (T<sub>H</sub>2) and mast cells, signals B cells to differentiate into plasma cells. IL-10 and CD40 interaction with T<sub>H</sub>2 cells then causes class switching to produce IgA.
Salivary IgA is produced by plasma cells in connective tissue around salivary glands. IgA in the alimentary system is produced by plasma cells in the lamina propria. It is the only Ig that can cross into the lumen of the alimentary tract. During lactation, the levels of IgA increase so that it becomes the predominant immunoglobulin in the milk (more than [[IgG]]). Mucosal epithelium have a “poly Ig receptor” and this bind to the J chain on the IgA, and allows IgA to travel across the cell. IgA crosses the cell in a transport vesicle and is released by exocytosis.
Salivary IgA is produced by plasma cells in connective tissue around salivary glands. IgA in the alimentary system is produced by plasma cells in the lamina propria. It is the only Ig that can cross into the lumen of the alimentary tract. During lactation, the levels of IgA increase so that it becomes the predominant immunoglobulin in the milk (more than [[IgG]]). Mucosal epithelium have a “poly Ig receptor” and this bind to the J chain on the IgA, and allows IgA to travel across the cell. IgA crosses the cell in a transport vesicle and is released by exocytosis.
[[Immunoglobulin M|Immunoglobulin M]]
[[Immunoglobulin M|Immunoglobulin M]]
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{{Jim Bee 2007}}
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[[Category:Immunoglobulins]]
[[Category:Immunoglobulins]]
[[Category:Image Review]]
[[Category:A&P Done]]